Holistic Approach to Concrete Technology for Major Bridges


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Title: Holistic Approach to Concrete Technology for Major Bridges

Author(s): B. C. Gerwick Jr..

Publication: Special Publication

Volume: 144


Appears on pages(s): 41-60

Keywords: bridge decks; bridges (structures); corrosion; tunnels; cracking (fracturing); cyclic loads; durability; fatigue (materials); finite element analysis; freeze-thaw durability; microcracking; reinforcing steels; salts; General

Date: 3/1/1994

Durability criteria for major bridges differ from those of most other structures in that, currently, major bridges are designed to serve for 100 to 125 years. Challenging this longevity are not only the normal physical and chemical attacks on the concrete itself and on the reinforcement, but also the intentional application of salts to highway bridge decks and, in the case of railroad and floating bridges, the accumulation of internal damage (fatigue) due to cyclic dynamic loading. Great progress has been made recently in identifying causes and finding preventive and mitigating measures aimed at specific phenomena. Advanced laboratory technology and equipment have been combined with field observations to describe the processes, prescribe tests for early diagnosis, and develop appropriate countermeasures. A number of tests of specific parameters have recently been developed and are now being implemented as mandatory criteria for concrete in major bridges designed for lives in excess of 100 years. Ever more refined linear elastic finite element analyses are being employed to reveal areas of probable cracking due to structural response. Rigid enforcement of specified quantitative criteria, focused on specific parameters, ignores the interactive complex processes involved. Excessive reliance on such criteria impedes rather than helps construction progress, and may on occasion be counterproductive to durability. What is required, instead, is a holistic systems approach that addresses not only individual processes and phenomena but their interaction.